diff --git a/requirements.txt b/requirements.txt
index 97dc7cd..1e5ebe2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,5 @@
 fastapi
 uvicorn
+testclient
+httpx
+pytest
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 0000000..c0edc2a
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,45 @@
+import pytest
+from fastapi.testclient import TestClient
+from src.app import app
+
+client = TestClient(app)
+
+def test_get_activities():
+    response = client.get("/activities")
+    assert response.status_code == 200
+    data = response.json()
+    assert isinstance(data, dict)
+    assert "Chess Club" in data
+
+def test_signup_for_activity():
+    email = "newstudent@mergington.edu"
+    activity = "Chess Club"
+    response = client.post(f"/activities/{activity}/signup?email={email}")
+    assert response.status_code == 200
+    assert email in response.json()["message"]
+    # Try signing up again (should fail)
+    response2 = client.post(f"/activities/{activity}/signup?email={email}")
+    assert response2.status_code == 400
+
+def test_unregister_from_activity():
+    email = "newstudent@mergington.edu"
+    activity = "Chess Club"
+    # Unregister
+    response = client.post(f"/activities/{activity}/unregister?email={email}")
+    assert response.status_code == 200
+    assert email in response.json()["message"]
+    # Try unregistering again (should fail)
+    response2 = client.post(f"/activities/{activity}/unregister?email={email}")
+    assert response2.status_code == 404
+
+def test_signup_invalid_activity():
+    response = client.post("/activities/Nonexistent/signup?email=test@mergington.edu")
+    assert response.status_code == 404
+
+def test_unregister_invalid_activity():
+    response = client.post("/activities/Nonexistent/unregister?email=test@mergington.edu")
+    assert response.status_code == 404
+
+def test_unregister_invalid_participant():
+    response = client.post("/activities/Chess Club/unregister?email=notfound@mergington.edu")
+    assert response.status_code == 404